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Fault slip in southern California

Louie, John N. and Allen, Clarence R. and Johnson, David C. and Haase, Paul C. and Cohn, Stephen N. (1985) Fault slip in southern California. Bulletin of the Seismological Society of America, 75 (3). pp. 811-833. ISSN 0037-1106.

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Measurements of slip on major faults in southern California have been performed over the past 18 yr using principally theodolite alignment arrays and tautwire extensometers. They provide geodetic control within a few hundred meters of the fault traces, which complements measurements made by other techniques at larger distances. Approximately constant slip rates of from 0.5 to 5 mm/yr over periods of several years have been found for the southwestern portion of the Garlock fault, the Banning and San Andreas faults in the Coachella Valley, the Coyote Creek fault, the Superstition Hills fault, and an unnamed fault 20 km west of El Centro. These slip rates are typically an order of magnitude below displacement rates that have been geodetically measured between points at greater distances from the fault traces. Exponentially decaying postseismic slip in the horizontal and vertical directions due to the 1979 Imperial Valley earthquake has been measured. It is similar in magnitude to the coseismic displacements. Analysis of seismic activity adjacent to slipping faults has shown that accumulated seismic moment is insufficient to explain either the constant or the decaying postseismic slip. Thus the mechanism of motion may differ from that of slipping faults in central California, which move at rates close to the plate motion and are accompanied by sufficient seismic moment. Seismic activity removed from the slipping faults in southern California may be driving their relatively aseismic motion.

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Additional Information:© 1985, by the Seismological Society of America. Manuscript received 12 July 1984. Creep and strain studies at the Seismological Laboratory have been funded for many years by the U.S. Geological Survey, most recently under Contract 14-08-0001-21212. One of the authors (J. L.) has also been supported by an AMOCO Foundation fellowship in geophysics. The authors appreciate the generous assistance from and useful discussions with Kerry Sieh, Hiroo Kanamori, Bill Stuart, John Lower, Holly Eissler, Richard Stead, and many members of the Laboratory too numerous to mention here. Creep monitoring was initiated by Ralph Gilman, whose efforts sustained the program for many years. The continuing efforts of Kate Hutton and Carl Johnson to maintain the quality of the SCARLET catalog has made much of the analysis possible. The authors are indebted to William Prescott of the U.S. Geological Survey for his unusually thoughtful review of the manuscript and many helpful suggestions. No measurements could have been undertaken without the kind cooperation of many landowners and agencies who granted permission to install monuments and instrumentation and allowed long-term access for maintenance and surveying.
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Caltech Division of Geological and Planetary Sciences4104
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Official Citation:John N. Louie, Clarence R. Allen, David C. Johnson, Paul C. Haase, and Stephen N. Cohn Fault slip in southern California Bulletin of the Seismological Society of America, June 1985, v. 75, p. 811-833
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:49161
Deposited By: Ruth Sustaita
Deposited On:03 Sep 2014 14:30
Last Modified:03 Oct 2019 07:11

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